1. Field of Invention
The present invention relates generally to semiconductor processing equipment. More particularly, the present invention relates to a relatively compact, detachable heat sink arrangement which enables heat generated by actuators to be absorbed by the heat sink arrangement substantially without requiring a significant tube arrangement to carry the heat from a wafer stage.
2. Description of the Related Art
For precision instruments such as photolithography machines which are used in semiconductor processing, factors which affect the performance, e.g., accuracy, of the precision instrument generally must be dealt with and, insofar as possible, eliminated. When the performance of a precision instrument is adversely affected, as for example by disturbance forces or by excessive heat, products formed using the precision instrument may be improperly formed and, hence, defective. For instance, a photolithography machine which is subjected to disturbance forces may cause an image projected by the photolithography machine to move, and, as a result, be aligned incorrectly on a projection surface such as a semiconductor wafer surface.
Scanning stages such as wafer scanning stages and reticle scanning stages are often used in semiconductor fabrication processes, and may be included in various photolithography and exposure apparatuses. Wafer scanning stages are generally used to position a semiconductor wafer such that portions of the wafer may be exposed as appropriate for masking or etching. Reticle scanning stages are generally used to accurately position a reticle or reticles for exposure over the semiconductor wafer. Patterns are generally resident on a reticle, which effectively serves as a mask or a negative for a wafer. When a reticle is positioned over a wafer as desired, a beam of light or a relatively broad beam of electrons may be collimated through a reduction lens, and provided to the reticle on which a thin metal pattern is placed. Portions of a light beam, for example, may be absorbed by the reticle while other portions pass through the reticle and are focused onto the wafer.
A stage such as a wafer scanning stage or a reticle scanning stage is typically supported by a base structure such that the stage may move in a linear direction. The base structure often includes or houses various sensors and actuators which serve to control the motion of the stage and a table, e.g., a wafer table, which is a part of an overall stage apparatus. Such actuators are often arranged to control a coarse stage of an overall wafer stage, and include coils which generate heat. The heat generated by the coils may be relatively significant, e.g., significant enough to affect an exposure process performed using the overall wafer stage. The heat generated may result in a temperature rise of, for example, of approximately 10 degrees Celsius to approximately 20 degrees Celsius higher than a desired ambient temperature. Since the heat generated by the coils may adversely affect the performance of the overall wafer stage, the generated heat is generally carried away or otherwise removed from the vicinity of relatively critical components of the overall wafer stage. Carrying heat away from relatively critical components, as for example a wafer, reduces the effect of excessive heat on the critical components.
In order to effectively conduct heat away from critical components of an overall wafer stage, tubes are often incorporated into overall wafer stage designs. The tubes may be arranged to carry coolant from a coolant supply or source effectively to the heat generating coils in order to allow the generated heat to be carried away from the heat generating coils by the coolant. Often, multiple tubes which are relatively long may wind from an external coolant supply through the overall wafer stage. Coolant which has effectively absorbed the generated heat may then pass through the tubes to an external cooling system which may cool the coolant or otherwise remove the heat from the coolant.
While the use of multiple tubes which carry coolant is effective in transferring heat away from critical components of an overall wafer stage system, e.g., a precision stage system, the use of tubes often introduces disturbances within the system. Such disturbances, which may be relatively large, generally include disturbance forces. The disturbance forces may be caused when tubes are pulled as precision stages move. In other words, tube drag may give rise to significant disturbance forces. Both tube drag and disturbance forces may create problems within the precision stage system. For instance, the accuracy with which the precision stages may be positioned may be compromised, particularly when disturbance forces are relatively large and have a significant effect on the positioning of a wafer.
Therefore, what is needed is a method and an apparatus for reducing the effect of heat generated by coils within an overall stage apparatus. That is, what is desired is a method and an apparatus for carrying heat away from coils associated with an overall stage apparatus substantially without introducing significant disturbance forces within the overall stage apparatus.